Urinary tract infections are quite common and left untreated may lead to permanent kidney scarring. The bacteria most often responsible for human UTI are the members of the Enterobacteriaceae. E. coli isolates from human UTI's often have the ability to adhere to uroepithelium and agglutinate human erythrocytes in vitro; this adherence is mediated by special hair-like appendages called pili. These UTI-associated pili are distinguished from Type I, or common, pili on the basis of hemagglutination not inhibited by D-mannose. Uropathogenic E. coli also are often resistant to the bactericidal activity of human serum; this property may help the bacteria to successfully infect the urinary tract. It has recently been demonstrated that some, but not all plasmids tested confer a greater serum resistance to E. coli. At this time it has not been well documented if other gram-negative enterics pathogenic for the human urinary tract also possess either of these two virulence properties. The proposed research will: (1) identify adherence factors of humant UT pathogens by screening clinical isolates for agglutination of human and animal erythrocytes and monkey kidney cells; (2) determine if the same or similar gene sequences for UTI-associated D-mannose resistant pili from E. coli are also found in other gram-negative enterics causing UTI, by using radiolabeled DNA probe prepared from the cloned gene of mannose-resistant pili from a nephropathogenic E. coli; (3) measure the frequency of serum resistance among uropathogenic Enterobacteriaceae in a microtiter assay; and (4) determine the role of plasmids, if any, in contributing to these virulence facrors, by screening isolates for common plasmids or common restriction-endonuclease generated fragments, such as those identified as conferring serum resistance from the E. coli plasmids R6-5 and Col V,I-K94.